1. Field of the Invention
The invention relates generally to field effect devices. More particularly, the invention relates to field effect devices with enhanced performance.
2. Description of the Related Art
Semiconductor structures generally include semiconductor devices such as but not limited to resistors, transistors, capacitors and diodes. The semiconductor devices are connected and interconnected with patterned conductor layers that are separated by dielectric layers. In turn, the patterned conductor layers and dielectric layers are also located and formed over a semiconductor substrate.
Of the foregoing semiconductor devices, transistors, and in particular field effect transistors are particularly common. Field effect transistors have been successfully scaled over the period of several decades to provide enhanced integration levels and enhanced performance levels of integrated circuits.
Of the more recent advances in field effect device technology is the use of generally high doelectric constant materials (i.e., having a dielectric constant greater than about 20) and metal gate (i.e., metal, metal alloy and metal nitride) gate materials. Generally high dielectric constant gate dielectric materials are desirable insofar as generally higher dielectric constant gate dielectric materials provide for thicker gate dielectrics which are readily manufacturable, while providing comparable performance in comparison with generally lower dielectric constant gate dielectric materials. Metal gate materials are desirable insofar as metal gate materials provide for an opportunity to engineer and tune a work function within a particular field effect device that uses a particular metal gate.
While field effect transistor devices are common and ubiquitous within semiconductor circuit fabrication, field effect transistor devices are nonetheless not entirely without problems.
In particular, it is often difficult to fabricate field effect transistor devices with enhanced performance within semiconductor circuits.
Since field effect transistors are likely to continue to be prevalent within the semiconductor fabrication art, desirable are field effect transistor devices and methods for fabricating the same that provide for enhanced field effect transistor device performance, in particular at decreased dimensions.